Cathode arrangement for x-ray tubes



My 9 w29, M. w. DAUMANN CATHODE ARRANGEMENT FOR X-RAY TUBES Filed Jan. l5, 1924 Patented July 9, 1929.

UNITED STATES 1,720,210 PATENT OFFICE.

KARL WILHELM DAUMANN, OF HAMBURG, GERMANY.

CATHODE RRANGEMENT FOR X-RAY TUBES.

Application filed January 15, 1924, Serial No. 686,299, and in Germany January 11, 1923.

M v invention relates to X-ray tubes and particularly to the cathodes oli such tubes, and has -l'or ils object lo provide a lilamcntalv cathode for such tubes which will be particularly suitable for the purpose of diagnosis. `When X-ray tubes are used for such a purpose it is desirable to have a focus of very small dimensions, that is to say, as nearly as possible a focal point, so tliat the il@ X-rays may produce sharp images. Of course the use ot' a focal point places a great strain on the anticathode; in order to avoid or vreduce this strain, it has been proposed to employ a vfocal band or strip. in such a l5 manner as to give it the ctl'ect of a point by a sort of -torcshortcning. lln practice, however, it has been found rather dilicult to obtain a focal strip of sufficient sharpness by means of the cathode, and this diliculty has been particularly great in the case oit' X-ray tubes employing ilamentary heated cathodcs.

The invention relates to a novel construction of a cathode of the above indicated character. By my novel construction ol the cathode and by the novel relative arrangement of the heated ,filament and oi? a collector associated therewith, il have secured very supe-rior results which fully answer all the requirements, as has been proved by elabil@ crate experiments.

According to my present invention the heated cathode consists of an elongated heated wire or filament located at or near the apex of two surfaces of the collector which converge toward a line parallel to the longitudinal axis of the cathode, or coincident with such axis. Preferably this elongated 'heated cathode has` the shape of a closely wound coiled spring which tits into a slit at te the apex of said collector surfaces, illin 'said slit almost entirely, there being lett' an amount of play just sucient for the inscr-A tion or removal of 'such filament. ,'lhese two converging surfaces of the obllector,

a5 which extend lengthwise of the axis of the filament, are preferably used in conjunction with transverse surfaces at the ends of the collector and of the cathode, to prevent the escape of electrons lengthwise of the cathode.

' A typical and satisfactory embodiment of this invention isV illustrated by the accompanying drawings in which Fig. 1 is a longitudinal section through a portion of an X-ray tube embodying my invention; Fig. 2 is a longitudinalsection taken in a plane at right angles to Fig. 1 and Fig. 3 is a face view of the collector, the cathode, and associated parts.

In the cmbmlimcnt illustrated, the elongated heated cathode l has the shape of a closely wound coil very much like a coiled spring, this coil being connected with, and carried by, the ends oi wires 2 and 3 which serve for supplying current in any well known or approved manner for the purpose of heating the cathode. The latter is situated within an opening or slit 4, located be tween the adjacent longitudinal edges of the two converging surfaces 5 and 6 of the collector. T he line in which said surfaces it' continued would intersect, is parallel to the longitudinal axis of the cathode 1, or may coincide therewith; that is to say, the cathode 1 is located at or near the apex of the surfaces 5 and 6. As shown, the cathode lills the opening or slit l almost entirely, leaving only suflicient play for the convenient insertion and removal of the cathode. At both ends of the cathode 1, there are placed transverse surfaces 7 and 8 extending from one of the converging surfaces 5 and 6 to the other, and preferably these end surfaces 7 and 8 also converge toward the cathode. The `line in which the sur laces 7 .and 8 il continued would intersect, is transverse to the longitudinal axisv ot the cathode l. The purpose of these end surfaces 7 and 8 oli the collector is to prevent the escape of electrons from the ends o'l the longitudinal trough `formed by the converging surfaces 5 and 6. The four surfaces 5, 6, 7, 8 thus form a unit in the shape of'a hip-roof or of a box open at the wide end, and having at the narrow end a slit in which the cathode is situated. This box-like collector is supported by means of a trough-like body 11, the bottom of which also constitutes a screen to prevent the escape or scattering of electrons from the cathode in a direction away from the collector (that is to say, downwardly in Figs. 1 and 2). This support 11 is made oi metal and is preferably connected with the collector to form a unit carried by supporting wires 9 and 10 suitably attached to the body of the X-ray tube.

The wires 2 and which supply the current to the cathode 1, pass through insulating tubes 12 and 13, made of glass or other suitable material/and extending through the trough 11.

The arrangement of cathode and collector described above is very efficient in producing a focal strip or band ot' X-rays which, when utilized in a direction oblique with reference to the axis of the filament, will have the effect of a focal point so that ima-ges of great sharpness Will be roduced.

The filament l is adapted to he heated to incandescence by the electric current supplied through the wires 2 and 3. The screening body ortrough 11, together with the collector walls 5, 6, 7, 8, compels the electrons to escape in one direction only, that is, through the open end of the collector, which open end faces away from the screening body 11.

Various modilications .may be made Without departing trom the spirit ot' my invention as set forth in the appended claims.

I claim:

l. A cathode arrangement for X-ray tubes, comprising an elongated filament having connections for passing an electric current therethrough and adapted to be heated to incandescence by such current and a collector elongated in the same direction as said iilam-ent and having converging surfaces at or near the apex of which said ilamentis located, said surfaces converging toward a lline which is parallel to the longitudinal axis ot the filament or coincides with such axis.

2. A cathode arrangement for X-ray tubes, comprising an elongated lilamcnt having connections for passing an electrical current therethrough and adapted to be heated to incandescence by such current, and a collector elongated in the saine direction as said tilament and having converging surfaces spaced adjacent to their apex to form an opening in which said filament is located, said surfaces converging toward a line which is parallel to the longitudinal axis et the filament or coincides with such axis.

3. A cathode arrangement tor X-ray tubes, comprising an elongated filament having connections for passing an electric current therethrough and adapted to be heated to incandescence by such current, said filament being coiled about its longitudinal axis, and acollector elongated in the same direction as said filament and having surfaces converging toward a line which is parallel or coincident with the'said filament axis.

4. A lcathode arrangement for X-ray tubes, comprising an elongated filament having connections for passing an electrical current therethrough and adapted to be heated to incandescence by such current, and a collector elongated in the same direction as said filament and having converging surfaces spaced adjacent to their apex to form an elongated opening in which said lilament is located, said surfaces converging-toward a line which is parallel to the longitudinal axis ot the filament or coincides with such axis, the said filament forming a coil which lills said opening almost entirely.

5. A cathode arrangement :tor X-ray tubes, comprising an elongated filament having connections for supplying an yelectric current thereto and adapted to be heated to incandescence by such current, a screening body located on one side of said filament, and a. collector elongated in the same direction as saidlilament and located adjacent to the filament and open on that side of the filament which is opposite to the one on which the screening body is arranged.

6. A cathode arrangement for X-ray tubes, comprising an elongated iilament having connections for supplying an electric current thereto, and adapted to be heated to incandescence by such current, and a collector comprising two Surfaces which converge toward a line which is parallel to the longitudinal axis of the filament, and also comprising tWo surfaces located at the ends of the first mentioned surfaces and converging toward a line which is transverse to the longitudinal axis of the filament. l

In testimony whereof I have signed this specification.

KARL "WILHELM DA'UMANN. 

